U.S. patent application number 17/452655 was filed with the patent office on 2022-03-31 for liquid pressure reducing valve.
This patent application is currently assigned to POLYMER TECHNOLOGIES LIMITED. The applicant listed for this patent is POLYMER TECHNOLGIES LIMITED. Invention is credited to David TAYLOR.
Application Number | 20220099204 17/452655 |
Document ID | / |
Family ID | 1000006061043 |
Filed Date | 2022-03-31 |
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United States Patent
Application |
20220099204 |
Kind Code |
A1 |
TAYLOR; David |
March 31, 2022 |
LIQUID PRESSURE REDUCING VALVE
Abstract
A fluid pressure reducing valve apparatus includes a pressure
reducing valve. The valve has: a body containing a fluid-flow
chamber, a liquid supply orifice into the chamber, a liquid outlet
from the chamber, a regulation plate opposed to the orifice, a
spring acting to urge the plate towards the orifice, and a
diaphragm between the plate and the body to close the chamber
between them. A controllable motor drive acts between the body and
an end of the spring remote from the plate. A flow meter is
positioned downstream of the outlet. A controller is arranged to
receive flow data from the flow meter and to control the motor
drive for withdrawal of the remote end of the spring in accordance
with flow rate measured by the flow meter. For an increase in
demand flow, the plate is partially withdrawn to maintain
downstream pressure on such increase and vice versa.
Inventors: |
TAYLOR; David; (Portsmouth,
GB) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
POLYMER TECHNOLGIES LIMITED |
St. Helier |
|
JE |
|
|
Assignee: |
POLYMER TECHNOLOGIES
LIMITED
St. Helier
JE
|
Family ID: |
1000006061043 |
Appl. No.: |
17/452655 |
Filed: |
October 28, 2021 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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PCT/EP2021/062071 |
May 6, 2021 |
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17452655 |
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PCT/GB2020/052750 |
Oct 30, 2020 |
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PCT/EP2021/062071 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F16K 37/005 20130101;
F16K 17/0453 20130101; F16K 31/04 20130101; E03B 7/075 20130101;
F16K 31/50 20130101; F16K 17/048 20130101; E03B 7/072 20130101 |
International
Class: |
F16K 17/04 20060101
F16K017/04; F16K 31/50 20060101 F16K031/50; F16K 31/04 20060101
F16K031/04; F16K 37/00 20060101 F16K037/00; E03B 7/07 20060101
E03B007/07 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 4, 2019 |
GB |
1916022.5 |
Claims
1. A fluid pressure reducing valve apparatus comprising: a spring
loaded pressure reducing valve having: a body containing a
fluid-flow chamber, a liquid supply orifice into the chamber and a
liquid outlet from the chamber, a regulation plate opposed to the
orifice and subject in use to supply liquid acting on it, a spring
acting to urge the plate towards to the orifice and a diaphragm
between the regulation plate and the body to close the chamber
between them and subject in use to regulated pressure in the
chamber a controllable motor drive acting between the body and an
end of the spring remote from the regulation plate, a flow meter
downstream of the outlet and a controller arranged to receive flow
data from the flow meter and to control the motor drive for
withdrawal of the remote end of the spring in accordance with flow
rate measured by the flow meter; the arrangement being such that in
use for increase in demand flow, the regulator plate is partially
withdrawn to maintain downstream pressure on such increase and vice
versa.
2. A fluid pressure reducing valve apparatus as claimed in claim 1
wherein the body has an interior void partitioned by the diaphragm
into the fluid-flow chamber on one side of the diaphragm and a dry
chamber on the other side of the diaphragm.
3. A fluid pressure reducing valve apparatus as claimed in claim 1,
wherein (i) the apparatus is adapted for reducing the pressure of
water; or (ii) the apparatus is adapted for reducing the pressure
of hydrocarbon fluids both liquid and gaseous.
4. A fluid pressure reducing valve apparatus as claimed in claim 1,
wherein the controllable motor drive is a servo motor drive.
5. A fluid pressure reducing valve apparatus as claimed in claim 4,
wherein the controller is adapted for calculation of the servo
motor action in spring positioning in accordance with a
substantially linear downstream pressure and flow rate
relationship.
6. A fluid pressure reducing valve apparatus as claimed in claim 5,
wherein the calculation is based on servo positioning of the spring
alone.
7. A fluid pressure reducing valve apparatus as claimed in claim 6,
wherein the calculation is based on a lookup table of downstream
pressures and flow rates.
8. A fluid pressure reducing valve apparatus as claimed in claim 7,
wherein the lookup table includes values of pressure to be
achieved.
9. A fluid pressure reducing valve apparatus as claimed in claim 8,
wherein the lookup table includes spring positions in terms of
servo revolutions.
10. A fluid pressure reducing valve apparatus as claimed in claim
1, wherein the regulation plate is provided in abutment with a
central region of the diaphragm, with a guide rod extending into a
centring guide in the orifice.
11. A fluid pressure reducing valve apparatus as claimed in claim
1, wherein the regulation plate is provided spaced from the
diaphragm, on a guide rod extending from the diaphragm into a
centring guide in the orifice.
12. A fluid pressure reducing valve apparatus as claimed in claim
1, wherein the spring is a compression spring acting on the side of
the diaphragm remote from the orifice.
13. A fluid pressure reducing valve apparatus as claimed in claim
1, wherein the spring is a tension spring acting on the side of the
diaphragm near to the orifice.
14. A fluid pressure reducing valve apparatus as claimed in claim
1, wherein the controllable motor drive includes a nut and lead
screw device arranged to act on the spring at an end remote from
diaphragm and actuatable by a motor of the drive.
15. A fluid pressure reducing valve apparatus as claimed in claim 1
in combination with a remote pressure sensor for measuring
downstream pressure to be maintained.
16. A fluid pressure reducing valve apparatus comprising: a spring
loaded pressure reducing valve having: a body having an interior
void partitioned by a diaphragm into a fluid-flow chamber on one
side of the diaphragm and a dry chamber on the other side of the
diaphragm, a fluid supply orifice into the fluid-flow chamber and a
fluid outlet from the fluid-flow chamber, a regulation plate
opposed to the orifice and subject in use to supply fluid acting on
it, the regulation plate being connected directly or via a
connecting element to the said one side of the diaphragm, and the
diaphragm in use being subject in use to regulated pressure in the
fluid-flow chamber a compression spring located in the dry chamber
on the said other side of the diaphragm, the compression spring
being arranged so as to apply pressure through the diaphragm to
urge the plate towards the orifice and a controllable motor drive
acting between the body and an end of the compression spring remote
from the regulation plate, a flow meter downstream of the outlet; a
controller and an electronic data store held within or being in
communication with the controller, the data store containing data
defining a relationship between fluid flow rate and fluid pressure
in a downstream pipe network to which the pressure reducing valve
is connected; the controller being arranged to receive flow data
from the flow meter and to control the motor drive for withdrawal
or advancement of the remote end of the spring in accordance with
the flow rate measured by the flow meter and the relationship
between fluid flow and fluid pressure thereby to vary the position
of the regulator plate and fluid flow through the fluid supply
orifice to maintain a desired downstream fluid pressure.
17. A fluid pressure reducing valve apparatus comprising a spring
loaded pressure reducing valve, a controllable motor drive, a flow
meter and controller as defined in claim 1, wherein the fluid
pressure reducing valve apparatus is linked (e.g. wirelessly) to a
remote control facility, from which remote control facility, the
operation of the apparatus can be remotely controlled.
18. A water supply system, the water supply system comprising a
plurality of local networks, each of the local networks being
provided with a pressure reducing valve apparatus as defined in
claim 1.
19. A method of controlling the water pressure in a local water
network having a pressure reducing valve connecting the local water
network to a high pressure mains supply, the method comprising: (i)
providing the pressure reducing valve with a motorised actuator
that can vary the flow of water into the network upon receipt of
control signals from a controller; (ii) providing the network with
a flow meter and pressure sensor downstream (e.g. immediately
downstream) of the pressure reducing valve, the flow meter and
sensor being in communication with the controller; (iii) measuring
flow rates and pressures to establish a relationship between flow
rate and pressure of water flowing into the network, and storing
data establishing the relationship in the controller and/or a
remote control location; (iv) using the said relationship to
establish a pressure reducing valve setting at a given time point
which maintains a desired minimum pressure at a defined remote
location in the network; and (v) monitoring changes in the flow
rate in the network detected by the flow meter and actuating the
motorised actuator to change the pressure reducing valve setting in
response to the changes in the flow rate in order to maintain the
desired minimum pressure at the defined remote location in the
network.
20. A method according to claim 19 wherein the pressure reducing
valve is as defined in claim 1.
Description
CROSS REFERENCES TO RELATED APPLICATIONS
[0001] This application is based on, and claims priority to, PCT
Patent Application No.: PCT/EP2021/062071, filed on May 6, 2021;
PCT Patent Application No.: PCT/GB2020/052750, filed on Oct. 30,
2020; and United Kingdom Patent Application No.: 1916022.5, filed
on Nov. 4, 2019. The contents of the prior applications are hereby
incorporated by reference herein in their entirety.
TECHNICAL FIELD
[0002] The present invention relates to a liquid pressure reducing
valve, particularly though not exclusively for water mains.
BACKGROUND
[0003] Water supply networks typically comprise a high pressure
regional mains network connected to a plurality of local networks.
Water pressures in the high pressure mains supply are generally too
high for consumers in the local networks and therefore pressure
reducing valves are positioned at the interface between the high
pressure main and the local network to reduce the pressures.
[0004] A typical pressure reducing valve (PRV) comprises a chamber
having an inlet connected to the high pressure mains and an outlet
connected to the local network. Typically, the valve has two
chambers, an upper and a lower chamber separated by a diaphragm.
Water passes through the PRV via the lower chamber. A reduced
downstream pressure is achieved by allowing a hydraulic connection
between the upstream pressure and the upper chamber of the PRV. In
this hydraulic system the water from the upstream side passes
through a pilot valve with a spring-loaded governor arrangement to
allow water to escape from the upper chamber if the pressure in the
upper chamber exceeds a predetermined level. More sophisticated
conventional PRV's incorporate further hydraulic circuits to give
more accurate control of the downstream pressure using various
arrangements of differential control valves. A spring can be
included in the upper chamber to provide a better seal when the
upstream pressure is allowed unhindered into the upper chamber in
order to completely close the valve.
[0005] Loss of water from mains is a problem due to the age of
mains pipework and damage to mains and associated equipment. Many
mains are old and have multiple leaks. Even newer mains can suffer
leaks. Leak flow is greatest when the water pressure is highest,
unsurprisingly.
[0006] A problem with such conventional PRV's setting the spring in
a pressure reducing valve at the entrance to the local network with
a substantially constant water pressure entering the network is
that, for much of the time, when demand is lower, the local network
will be over-pressurised. This will in turn exacerbate the problem
of leakage.
[0007] Various proposals have been made for pressure reducing
valves where the biasing force applied (e.g. by a spring) to the
regulator plate or valve element can be varied automatically to
accommodate changing levels of demand within the local network and
thereby remove or alleviate the problem of over-pressurisation.
[0008] For example, GB 2,176,316 (NRDC) discloses an apparatus
which is described in the abstract in the following terms:
[0009] Apparatus for controlling the flow of water through a pipe
(26) including a valve (29) and an orifice plate (37) and supplying
a water distribution system comprises a governor (1) actuating a
pilot valve (14) in a servo system controlling the valve (29). The
governor (1) has two diaphragms (5) and 6) linked by a tension
spring (7) the extension of which is determined by the rate of flow
through the orifice plate (37). The first diaphragm (5) operates a
valve member (13) of the pilot valve (14) and is subjected to the
differential pressure caused by flow through the orifice plate
(37). The second diaphragm (6) is loaded by a compression spring
(8) and its displacement is dependent upon the control pressure at
a tapping (38) in the pipe (26). The movement of the valve member
(14) is the combination of the displacements of the two diaphragms
(5 and 6), and raises the control pressure at tapping (38) when
demand for water increases.
[0010] GB 2165372 (TLV Co. Ltd) discloses a pressure reducing valve
with a pressure-setting spring linked to an actuator which can
change the force setting of the spring in response in the event
that the difference between the pressure on the downstream side of
the pressure reducing valve and a desired target pressure exceeds a
certain value.
[0011] EP1762922 (R. Nussbaum AG) discloses a pressure reducing
valve having a spring biased valve element which controls flow of
liquid through a supply aperture leading to a chamber having a
liquid outlet. The valve has an electromechanical actuator which
can vary the force setting of the spring in response to changes in
water pressure downstream of the pressure reducing valve.
[0012] WO 03/057998 (Optimus Water Technologies Ltd)) discloses an
hydraulically controlled PRV, the operation of which is controlled
by a complex hydraulic arrangement comprising a filter unit, flow
restriction orifice, pilot valve and differential control valve
(DCV) as well as the pressure reducing valve (PRV). A bypass pipe
diverts a small proportion of the water entering the PRV through a
control circuit linking the pilot valve and DRV. A branch pipe
upstream of the pilot valve is connected to the pressure reducing
valve but enters a pressure chamber containing the spring on the
opposite side of the diaphragm from the regulator valve. Thus, in
the PRV of WO 03/057998, there are "wet chambers" both sides of the
diaphragm. The PRV of WO 03/057998 is not provided with an actuator
for adjusting the spring pressure. Instead, the DCV is provided
with an actuator which is responsive to pressure signals received
from a controller and it is the DCV that refines the operation of
the PRV. The water pressure control arrangement described in WO
03/057998 would appear to suffer from a number of potential
disadvantages. Firstly the hydraulic control system is overly
complex and there are more components that can go wrong. Secondly,
the presumably narrow bore bypass tubes are likely to be more
susceptible to blockage and/or freezing up, thereby interfering
with or stopping the control function. Thirdly, in the PRV, both
sides of the diaphragm are exposed to water meaning that the spring
will presumably be permanently surrounded by water, with the
consequent possibility of lime-scale accretion occurring to the
spring itself which could affect the ability of the valve to
completely close if or when required.
BRIEF DESCRIPTION
[0013] An object of the present invention is to provide an improved
liquid pressure reducing valve which overcomes or at least
alleviates the problems in known pressure reducing valves as
described above.
[0014] The present inventor has noted a simple correlation between
on the one hand pressure required downstream of a pressure reducing
valve to maintain a given minimum pressure at a remote point of a
local network, the pressure reducing valve being between a high
pressure regional supply and the local network, and on the other
hand flow in the local network. Both the required regulated
pressure and the flow on the downstream side of the pressure
reducing valve appear to be normally linearly related. Despite
this, the present inventor is not aware of any pressure reducing
valves controlled in accordance with flow through them, except for
the somewhat complex arrangement disclosed in GB 2,176,316.
[0015] According to one aspect of the invention, there is provided
a fluid pressure reducing valve apparatus comprising: [0016] a
spring loaded pressure reducing valve having: [0017] a body
containing a fluid flow chamber, [0018] a fluid supply orifice into
the chamber and a liquid outlet from the chamber, [0019] a
regulation plate opposed to the orifice and subject in use to
supply fluid acting on it, [0020] a spring acting to urge the plate
towards to the orifice and [0021] a diaphragm between the
regulation plate and the body to close the chamber between them and
subject in use to regulated pressure in the chamber; [0022] a
controllable motor drive acting between the body and an end of the
spring remote from the regulation plate, [0023] a flow meter
downstream of the outlet and [0024] a controller arranged to
receive flow data from the flow meter and to control the servo
motor for withdrawal of the remote end of the spring in accordance
with flow rate measured by the flow meter; the arrangement being
such that in use for increase in demand flow, the regulator plate
is partially withdrawn to maintain downstream pressure on such
increase and vice versa.
[0025] The body may have an interior void partitioned by the
diaphragm into a fluid-flow chamber on one side of the diaphragm
and a dry chamber on the other side of the diaphragm, wherein the
fluid-flow chamber is provided with the fluid supply orifice into
the chamber and a liquid outlet. By dry chamber is meant that the
interior of the chamber does not come into contact with the fluid.
This is in contrast to the pressure reducing valve disclosed in WO
03/057998 where both chambers either side of the diaphragm in the
PRV are "wet" chambers; i.e. are exposed to the fluid (in that case
water).
[0026] The fluid pressure reducing valve apparatus may further
comprise an electronic data store held within or being in
communication with the controller, the data store containing data
defining a relationship between fluid flow rate and fluid pressure
in a downstream pipe network to which the pressure reducing valve
is connected.
[0027] Thus, the controller may be arranged to receive flow data
from the flow meter and to control the motor drive for withdrawal
or advancement of the remote end of the spring in accordance with
the flow rate measured by the flow meter and the relationship
between fluid flow and fluid pressure thereby to vary the position
of the regulator plate and fluid flow through the fluid supply
orifice to maintain a desired downstream fluid pressure.
[0028] In a second aspect, the invention provides a fluid pressure
reducing valve apparatus comprising: [0029] a spring loaded
pressure reducing valve having: [0030] a body having an interior
void partitioned by a diaphragm into a fluid-flow chamber on one
side of the diaphragm and a dry chamber on the other side of the
diaphragm, [0031] a fluid supply orifice into the fluid-flow
chamber and a fluid outlet from the fluid-flow chamber, [0032] a
regulation plate opposed to the orifice and subject in use to
supply fluid acting on it, the regulation plate being connected
directly or via a connecting element to the said one side of the
diaphragm, and the diaphragm in use being subject in use to
regulated pressure in the fluid-flow chamber [0033] a compression
spring located in the dry chamber on the said other side of the
diaphragm, the compression spring being arranged so as to apply
pressure through the diaphragm to urge the plate towards the
orifice and [0034] a controllable motor drive acting between the
body and an end of the compression spring remote from the
regulation plate, [0035] a flow meter downstream of the outlet;
[0036] a controller and an electronic data store held within or
being in communication with the controller, the data store
containing data defining a relationship between fluid flow rate and
fluid pressure in a downstream pipe network to which the pressure
reducing valve is connected; [0037] the controller being arranged
to receive flow data from the flow meter and to control the motor
drive for withdrawal or advancement of the remote end of the spring
in accordance with the flow rate measured by the flow meter and the
relationship between fluid flow and fluid pressure thereby to vary
the position of the regulator plate and fluid flow through the
fluid supply orifice to maintain a desired downstream fluid
pressure.
[0038] Preferably the controllable motor drive is a servo motor
drive.
[0039] The fluid may be a liquid or gas.
[0040] In one general embodiment, the fluid is a liquid.
[0041] In another general embodiment, the fluid is a gas such as a
gaseous hydrocarbon.
[0042] When the fluid is a liquid, it may for example be water or a
liquid hydrocarbon.
[0043] In one particular embodiment, the fluid is water.
[0044] In another particular embodiment, the fluid is a liquid
hydrocarbon.
[0045] The invention is particularly applicable to water mains. It
is envisaged that the invention will also be applicable to
hydrocarbon fluids both liquid and gaseous in form.
[0046] The controller can be adapted for calculation of the server
motor action in spring positioning in accordance with a
substantially linear downstream pressure and flow rate
relationship. The calculation can be based on pressure to be
achieved in terms of servo positioning of the spring; or on servo
positioning of the spring alone. Alternatively it can be adapted
for servo motor action in accordance with a lookup table of
downstream pressure and flow rate. Again, the lookup table can
include values of pressure to be achieved, but is preferably
includes spring positions in terms of servo revolutions.
[0047] When the fluid is water and the pressure reducing valve is
connected to a local water network, the controller can be
programmed, or instructed by a remote control centre, to vary the
flow rate so as to ensure that the minimum water pressure provided
to a remote user in the network (i.e. the user at which there is
the greatest pressure drop) is within the range from 0.5 Bar to 2
Bar. More usually, the controller is programmed, or instructed by a
remote control centre, to vary the flow rate so as to ensure that
the minimum water pressure provided to a remote user in the network
is within the range from 0.6 Bar to 1.5 Bar, more typically 0.7 Bar
to 1.2 Bar. In one embodiment, the minimum water pressure provided
to a remote user in the network is approximately 1 Bar.
[0048] The pressure reducing valve apparatus of the invention may
be connected to a remote control facility (which may be referred to
herein for convenience as a remote control room, even though it may
not be a room as such). Either or both of the flow meter and
controller may be connected to the remote control facility (remote
control room), for example by wireless communication.
[0049] In one embodiment, only the controller is connected to the
remote control facility.
[0050] In another, and preferred, embodiment, both the flow meter
and controller are connected to the remote control facility.
[0051] By connecting the pressure reducing valve apparatus of the
invention to a remote control room, it is possible for local
control of the apparatus to be overridden remotely (e.g. manually),
for various operational reasons, such as the detection of
abnormally high flows of fluid (e.g. a liquid such as water) in the
network that are indicative of a major leak, for example a burst
pipe.
[0052] The controller may be programmed to send alarm signals to
the remote control room if fluid flows exceed a certain threshold
level.
[0053] Accordingly, in a further embodiment, the invention provides
a fluid pressure reducing valve apparatus comprising a spring
loaded pressure reducing valve, a controllable motor drive, a flow
meter and controller as defined herein, wherein the wherein the
fluid pressure reducing valve apparatus is linked (e.g. wirelessly)
to a remote control facility, from which remote control facility,
the operation of the apparatus can be remotely controlled.
[0054] A local network will typically form part of a larger network
in which a plurality of lower pressure local network are each
connected to a high pressure main by a pressure reducing valve
apparatus of the invention.
[0055] Accordingly, in a still further embodiment, the invention
provides a water supply system, the water supply system comprising
a plurality of local networks, each of the local networks being
provided with a pressure reducing valve apparatus of the invention
as defined herein.
[0056] The water supply system typically comprises a remote control
facility (e.g. a Main Control Room) as hereinbefore defined to
which the controllers of each of the pressure reducing valve
apparatuses of the local networks are linked.
[0057] Additionally, or alternatively, the flow meters of each of
the pressure reducing valve apparatuses of the local networks may
be connected to the remote control facility.
[0058] In another embodiment, the invention provides a method of
controlling the water pressure in a local water network having a
pressure reducing valve connecting the local water network to a
high pressure mains supply, the method comprising:
[0059] providing the pressure reducing valve with a motorised
actuator that can vary the flow of water into the network upon
receipt of control signals from a controller;
(ii) providing the network with a flow meter and pressure sensor
downstream (e.g. immediately downstream) of the pressure reducing
valve, the flow meter and sensor being in communication with the
controller; (iii) measuring flow rates and pressures to establish a
relationship between flow rate and pressure of water flowing into
the network, and storing data establishing the relationship in the
controller and/or a remote control location; (iv) using the said
relationship to establish a pressure reducing valve setting at a
given time point which maintains a desired minimum pressure at a
defined remote location in the network; and (v) monitoring changes
in the flow rate in the network detected by the flow meter and
actuating the motorised actuator to change the pressure reducing
valve setting in response to the changes in the flow rate in order
to maintain the desired minimum pressure at the defined remote
location in the network.
[0060] The pressure reducing valve used in the above method is
preferably a pressure reducing valve in accordance with the
invention as defined and described herein.
DRAWINGS
[0061] FIG. 1 is FIG. 2 of prior proposal GB 2,176,316.
[0062] FIG. 2 is a diagrammatic, cross-sectional, side view of a
pressure reducing valve apparatus according to one embodiment of
the invention.
[0063] FIG. 3 is a schematic view showing the apparatus of FIG. 2
(but with a very slightly differently shaped upper casing)
connected to a controller which is also connected to a remote
pressure sensor.
[0064] FIG. 4 is a typical plot of pressure required to be applied
in a network for constant remote pressure with varying demand
flow.
[0065] FIG. 5 is a schematic view of a water supply network showing
a water main having a pressure reducing valve apparatus of the
invention and a local network comprising a plurality of customer
supply taps (and leaks) downstream of the reducing valve apparatus.
The reducing valve apparatus is linked to a linked to a main
control room.
[0066] FIG. 6 shows an algorithm used to control the operation of a
pressure reducing valve apparatus of the invention. In FIG. 6,
F.sup.D is the flow at peak demand, P.sup.R is the pressure
required at the remote user at the peak demand flow rate F.sup.D,
P.sup.D is the set pressure at F.sup.D to give the pressure
P.sup.R, F.sup.N and F.sup.N+1 are instantaneous flow rates,
P.sup.M and P.sup.M+1 are instantaneous pressures at the remote
user, and P.sup.N and P.sup.N+1 are instantaneous downstream
pressures.
[0067] FIGS. 7A-7D show graphs of pressure and flow rates over a
twenty four hour period in a water supply network incorporating a
pressure reducing valve apparatus of the invention. The pressure
and flow rates shown in the graphs are those needed to maintain a
water pressure of 1 bar at a remote location in the network. FIG.
7A shows the mains pressure (in Bars) on the upstream side of the
pressure reducing valve. FIG. 7B shows the flow rate in litres per
second as measured by a flow meter immediately downstream of the
pressure reducing valve. FIG. 7C shows the water pressure measured
by a pressure sensor immediately downstream of the pressure
reducing valve and the flow meter. FIG. 7D shows the superimposed
flow rate and pressure plots of FIGS. 7B and 7C.
[0068] FIG. 8 shows a comparison of the water pressures and water
flow rates downstream of a pressure reducing valve over an eleven
hour time period where the pressure reducing valve is of convention
type (dotted lines) or a pressure reducing valve apparatus of the
invention (solid lines). The pressures shown in the uppermost graph
are pressures (expressed as the head of water in metres) required
to maintain a water pressure of 1 Bar at the remote location in the
network.
DETAILED DESCRIPTION
[0069] To help understanding of the invention, specific embodiments
thereof will now be described by way of example and with reference
to the accompanying drawings FIGS. 1 to 8.
[0070] Referring to the drawings, a spring loaded pressure reducing
valve 1 has a body 2 containing a water flow chamber 3. An inlet 4
opens into the water flow chamber via an inlet orifice 5. The inlet
is connected to an elevated pressure water main 6. An outlet 7 from
the water flow chamber is connected to a network 8 of pipes for
local distribution of water to individual consumers. The valve has
a flow pressure regulation plate 9 arranged opposite the inlet
orifice 5. A diaphragm 10 is fastened to the plate 9 and radiates
from it to the body, forming a seal with upper and lower parts
11,12 of the body 2. Thus, the water flow chamber 3 is sealed
between the upper and lower parts. The space above the diaphragm is
a dry chamber; i.e. water does not flow into this space.
[0071] The regulation plate has a guide rod 14 extending down from
it into a guide 16 in the inlet orifice 5. The rod extends through
both the regulation plate and the diaphragm. At its top end, inside
the dry chamber, it carries a nut 17 bearing on a spring centring
washer 18 and a diaphragm sealing and clamping plate 19. The
arrangement keeps the regulation plate centred over the inlet
orifice 5.
[0072] In a variant, a separate regulation plate 109 opposite the
orifice is provided on the lower rod 14. The diaphragm keeps the
plate 9/109 centred over the orifice 5.
[0073] A compression spring 21 located in the dry chamber acts at
its lower end 22 on the top of the clamping plate 19. The spring is
kept compressed to a greater or lesser extent as explained below.
Thus, it stays located around the centring washer 18. Its upper end
23 abuts a spring drive member 24 at the end of a drive tube 25 of
a servo device 26. The drive tube is housed in a fixed tube 27 of
the servo device, fast with the upper part 11 of the valve body 2.
Remote from the spring a lead screw 28 is journalled for axial
alignment in the drive tube within the fixed tube. A motor 29 and
gearbox 30 are arranged to the drive the lead screw. A nut 31,
preferably a recirculating ball nut, is fast with the remote end of
the drive tube 25, with the latter keyed to the fixed tube against
rotation. Thus, the spring drive member can be advanced to further
compress the spring or retracted to relieve compression, by
respective rotation of the motor and the lead screw.
[0074] Downstream from the outlet 7, the pipework 8 of the local
distribution network extends. In it adjacent the outlet is a flow
meter 32 and a pressure sensor 33. These are electronically
connected to a controller 34. Also connected to the controller is a
remote pressure sensor 35 at the furthest point 36 of the pipework
8. The controller 34 is also connected to a remote main control
room 39. The main control room typically controls a plurality of
local distribution networks, each equipped with its own controller
and pressure reducing valve apparatus. As an alternative to each
local distribution network having its own controller, the operation
of the pressure reducing valves can be controlled directly from the
main control room.
[0075] Along the pipework, there are various leaks 37, which
increase in their flow rate with pressure and a number of user taps
38 etc. It is these which are the primary determinant of the flow
at the pressure regulator 1. If it were of the type permanently set
to a pressure maintaining sufficient pressure at the furthest point
36 in the network, the pressure would be such as to aggravate the
leaks 37 regardless of the user flow at the taps 38.
[0076] In this embodiment of the invention, the entire pressure
reducing valve apparatus includes not only the pressure reducing
valve 1 and the flow meter 32, but also the controller 38 for
controlling the regulator, via the servo motor, in accordance with
flow measured by the flow regulator and indeed the remote pressure
sensor 35, which is not strictly necessary for the invention.
[0077] Many local distribution networks such as the network 8 have
been previously measured and exhibit a pressure/flow characteristic
as shown in FIG. 4 when the regulator is set to provide the
required furthest point pressure for varying flows. The ideal low
pressure point 41 for zero flow seldom exists due to leaks. The
practical low pressure point 42 can be measured at night when user
demand is negligible. Other flow and pressure readings 43 can be
made during periods of more and less usage by adjusting the
pressure reducing valve to provide the sufficient furthest point
pressure.
[0078] In practice, the pressure flow plot is a substantially
straight line with a slope or gradient and an offset equivalent to
the zero flow offset. The plot can be represented by the
equation:
Pressure required at regulator=Zero flow pressure+measured
flow.times.plot gradient (in terms of pressure per unit flow).
[0079] This is surprising, because it might be expected that
adjustment of the regulator would alter the measured flow. However,
this is a second order effect because the primary determinant of
flow is user usage. The leak flow is small by comparison and kept
lower than it might be, by keeping the pressure in the network
lower than it would be, if were set to its value to ensure that its
furthest point sufficiency at maximum flow. This value results in
too much flow and too much leakage at all other flows.
[0080] The spring 21 in the pressure reducing valve acts against
the force exerted by the diaphragm 10, which is subject to the
pressure to be regulated, the upstream pressure force exerted
against the regulation plate 9 being substantially constant and
being small in comparison with the diaphragm force. Thus,
shortening of the spring by an amount proportional to the change in
pressure required can provide this change, bearing in mind that
only a small movement of the regulation plate is required for a
significant change in pressure drop at the orifice of the outlet.
Thus, for practical purposes, linear movement of the end of the
spring acted on by the servo motor causes a linear change in
regulated pressure. Accordingly, the controller can be set up to
move the spring end linearly in accordance with the flow.
[0081] If the zero flow pressure and the gradient of the measured
flow plot are not known, the controller can be set up to adjust the
regulated pressure periodically for different flows to establish
the pressures required to achieve the sufficient furthest away
point pressure. For this connection is made with the remote
pressure sensor 35 and the near pressure sensor 33, suitably
wirelessly in the former case.
[0082] The controller can be provided with a memory adapted to
record a map of pressure and flow as opposed to memorising merely
the offset and gradient and use this as a look-up table for the
pressure to which it should regulate the downstream pressure as a
function of measured flow.
[0083] The sensor 33 can be used to fine tune the servo motor
control to achieve the desired pressure in accordance with measured
flow.
[0084] The manner in which the apparatus of the invention is set up
to control water pressure in a network will now be described in
more detail with reference to FIGS. 5 to 8.
[0085] The pressure/flow characteristics of a local water supply
network will vary according to a number of variables such as the
length of pipework, the number of consumers, the number of leaks in
the network and the location of the most remote user. Therefore,
when setting up the apparatus of the invention, an initial step is
to establish a pressure/flow relationship for the network and, in
particular, to establish the flow rates into the network that are
necessary in order to maintain a desired water pressure at the most
remote user at various times during a twenty four hour period. To
do this, for a twenty four hour period, the flow rates and water
pressures are measured by flow meter 32 and pressure sensor 33 and
the water pressure at the remote user is measured by remote
pressure sensor 35 and adjusted where necessary using the pressure
reducing valve to maintain a desired minimum pressure at the remote
user. The pressure and flow data are communicated from the flow
meter and pressure sensors to the controller and a relationship
between the flow rate and pressure established as described
above.
[0086] A set of pressure and flow rate data for one local
distribution comprising the pressure reducing valve apparatus of
the invention is shown in Table 1 below.
[0087] In the table, the water pressure data for the upstream side
(i.e. high pressure main) of the pressure reducing valve are shown
in the columns headed I/L Pressure whereas the water pressures
downstream of the pressure reducing valve are shown in the columns
headed O/L Pressure. Pressure figures are given in both Bars and
Head of Water in metres. The flow rates (given in both cubic metres
per hour and litres per second) are the flow rates measured by the
flow meter 32. The data are the pressures required to maintain a
water pressure of 1 Bar at the remote user. The pressure and flow
rate profiles over a twenty four hour period are shown in FIGS. 7A
to 7D. The relationship between pressure and flow rate obtained
from the data is shown in the graph in FIG. 4.
TABLE-US-00001 TABLE 1 Flow I/L I/L O/L Litres O/L Flow m.sup.3
Pressure Pressure Pressure per Pressure Time per hour m head Bar m
head second Bar 0 5.50 54.92 5.38 26.575 1.5279 2.60435 1 4.80
53.76 5.27 25.42 1.3334 2.49116 2 4.60 53.43 5.24 25.09 1.2779
2.45882 3 4.70 53.60 5.25 25.255 1.3057 2.47499 4 5.30 54.59 5.35
26.245 1.4723 2.57201 5 6.30 56.24 5.51 27.895 1.7501 2.73371 6
7.70 58.55 5.74 30.205 2.1391 2.96009 7 8.90 60.53 5.93 32.185
2.4724 3.15413 8 8.50 59.87 5.87 31.525 2.3613 3.08945 9 7.30 57.89
5.67 29.545 2.0279 2.89541 10 7.30 57.89 5.67 29.545 2.0279 2.89541
11 7.80 58.71 5.75 30.37 2.1668 2.97626 12 8.20 59.37 5.82 31.03
2.278 3.04094 13 9.30 61.19 6.00 32.845 2.5835 3.21881 14 8.80
60.36 5.92 32.02 2.4446 3.13796 15 9.00 60.69 5.95 32.35 2.5002
3.1703 16 9.40 61.35 6.01 33.01 2.6113 3.23498 17 10.30 62.84 6.16
34.495 2.8613 3.38051 18 12.00 65.64 6.43 37.3 3.3336 3.6554 19
12.30 66.14 6.48 37.795 3.4169 3.70391 20 11.40 64.65 6.34 36.31
3.1669 3.55838 21 9.70 61.85 6.06 33.505 2.6947 3.28349 22 10.20
62.67 6.14 34.33 2.8336 3.36434 23 8.40 59.70 5.85 31.36 2.3335
3.07328 24 5.30 54.59 5.35 26.245 1.4723 2.57201
[0088] Applying the relationship Y=mX+c to the data and the graph
gives a gradient (m) of 1.65 and a theoretical low pressure point
(c) at zero flow rate of 17.5 (Head of Water in metres). However,
because in practice there is never a zero flow rate (e.g. because
of leaks), a practical low pressure point is a pressure of about 25
metres (Head of Water).
[0089] Once the pressure/flow relationship has been established
empirically as described above (although it is also possible to
derive a relationship by theoretical calculations), this
relationship serves as the basis for control of the pressure
reducing valve according to the algorithm shown in FIG. 6.
[0090] Thus, as shown in the algorithm in FIG. 6, the pressure
reducing valve is initially adjusted by using the servo motor to
position the spring 21 so that if the flow rate measured by the
flow meter 32 were the flow rate F.sup.D at peak demand, the water
pressure P.sup.D measured by sensor 33 would be such as to give the
desired minimum pressure P.sup.R at the remote location. Data are
then gathered for the actual flow rates into the downstream
pipework 8. A first flow rate measurement F.sup.N at time point 1
is taken and compared with the peak flow rate figure F.sup.D. If
F.sup.N is less than F.sup.D, then the water pressure is reduced by
actuating the servo motor to move the position of the spring drive
member 24 and spring 21 to increase the biassing force of the
spring against the regulation plate 9. At a second time point, the
flow rate is measured again to give a flow rate F.sup.N+1. If the
flow rate has fallen against, a further movement of the spring
drive member 24 and spring 21 to increase the biassing force of the
spring against the regulation plate 9 is effected so as to reduce
further the water pressure as measured by sensor 33. On the other
hand, if the flow rate F.sup.N+1 has increased, the spring drive
member 24 and spring 21 are moved in the reverse direction to
reduce the biassing force of the spring against the regulation
plate thereby to the increase the water pressure in the pipework 8.
Thus, by taking flow rate measurements at regular intervals and
comparing each new flow rate measurement F.sup.N+1 with its
preceding flow rate measurement, the water pressure in the pipework
8 can be constantly adjusted so that the pressure as measured by
the sensor 33 is kept to the minimum necessary to provide the
desired minimum pressure P.sup.R at the remote location 36.
[0091] In conventional local water supply networks, pressure
reducing valves are typically set up so that the water pressure
measured immediately downstream of the pressure reducing valve is
the minimum water pressure required to give a defined pressure at
remote location 36. As a result, the network is over-pressured for
much of the time with the result that, inter alia, water losses
through leakage are greatly increased. This problem is avoided
using the pressure reducing valve apparatus of the present
invention. The advantages of the pressure reducing valves of the
present invention compared to conventional pressure reducing valves
set up to provide a constant water pressure are illustrated by the
graphs shown in FIG. 8. The lower graph shows the flow rates at
various times of the day. The flow rates measured in a network
fitted with a conventional pressure reducing valve are shown as
dotted lines whereas the flow rates measured when the conventional
pressure reducing valve was replaced by a pressure reducing valve
apparatus of the invention are shown in solid lines. The uppermost
graph in FIG. 8 shows the water pressures within the network over
the same period. As can be seen, the water pressure in the network
fitted with a conventional PRV remains constant and therefore the
pressure is much higher than it needs to be. By contrast, the
pressure in the same network fitted with a pressure reducing
apparatus of the invention is significantly lower throughout the
time period tested but is still sufficient to maintain the desired
water pressure at the remote location.
[0092] In the network shown in FIG. 5, the controller 34 is linked
to a Main Control Room 39 (remote control room), a location from
which the network can be controlled remotely. The main control room
can be linked to a plurality of local networks fed by a high
pressure main, each of the local networks being provided with a
pressure reducing valve apparatus of the invention. Alternatively,
or additionally, the flow meters and pressure sensors in each local
network can be linked to the Main Control Room and alarm signals
generated in the Main Control Room if abnormal flow rates (e.g.
indicative of a major mains failure or major leaks such as burst
pipe) are detected. By linking the controller 34 to a remote
control room, remote control of the downstream pressures and flow
rates can be achieved, where required for operational purposes.
* * * * *